Initial support for network acls
get_all_network_acls now works properly
Removed extraneous comments.
Added support for associating and disassociating network ACLs and
subnets.
Added supoprt for replacing network acl entries.
Now properly populates NetworkAclEntry class with icmp & port range
options.
Removed unnecessary import of NetworkAclEntry.
Synchronize get_all_snapshots() with current version of API
Updated Opsworks to take advantage of VPC.
The name parameter is optional for the CopyImage API call of ec2.

Make the name parameter optional for the copy_image method. The default value is the same as that
of the source AMI being copied [1].

[1]: http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-query-CopyImage.html
Updated Opsworks docstrings to latest.
s3put: accept headers values containing "="

s3put tries to split headers on the "=" sign. Some headers include a "=" sign (e.g. max-age), and can't be used. 

This pull request splits on the first equal sign to support those.

Caveat: if a user uses the command correctly (`s3put --header "header1=value1 header2=value2"), they won't get an exception.
Merge branch 'release-2.12.0' into develop

* release-2.12.0:
  Bumping version to 2.12.0
Added dev release notes back in, as well as a template for future laziness.
Fixed the creation of EC2 VPC instances with public IPs.
Added Opsworks to the docs & cleaned up a bunch of Sphinx build errors.
Altered SDB to no longer cause errors when building the docs.
Merge branch 'opsworks-vpc' into develop
Updated release notes to mention the Opsworks VPC support.
SNS ``publish`` now uses POST.
Merge branch 'ec2-public-ip-fix' into develop